The boad, long term objective of this research is to investigate the molecular mechanisms underlying the broad, long term objective regulation and function of CCAAT/Enhancer Bin,clingProteindelta(C/EBPdelta), a member of the C/EBP family of nuclear proteins. Although experimental studies demonstrate that C/EBPdelta functions as a growth suppressor and clinical breast cancer studies correlate reduced C/EBPdelta levels with a poor prognosis, regulation and function of C/EBPdelta is incompletely understood. The specific aims of this proposal are: (1) investigate the role of specific transcription factors, co-activators, methyl-CpG binding proteins and chromatin remodeling complex components in the transcriptional activation of the C/EBPdelta gone; (2) investigate and identify proteins, protein modifications and protein degradation complexes that mediate C/EBPdelta post transcriptional and post translational regulation; (3) investigate the functional significance of C/EBPdelta interactions with key cell cycle regulatory proteins (Rb, E2F1 and p27); (4) investigate the transcriptional activator role of C/EBPdelta in growth control by identifying and characterizing C/EBPdelta regulated genes. The experimental techniques include protein/protein interaction assays, gene expression analyses and an innovative "CHIP on CHIP" assay. Our overall hypothesis is that C/EBPdelta plays a key role in cell growth control and that "loss of function" alterations in the C/EBPdelta gene promote neoplastic development. The health-relatedness of this research project lies in the novel growth suppressor function of C/EBPdelta, which is specific to the initiation and maintenance of GO growth arrest. Few GO genes have been identified and little is known about the regulation of GO. The proposed studies will provide a better understanding of the regulation and function of C/EBPdelta, and in doing so; provide a working model for other G0-specific genes and their potential role in tumorigenesis.